Machine-switching telephone-exchange system.



C. L. GOODRUM.

MACHlNE SWHCHING TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED OCT. 2. 1916.

Patented Aug. 28, 1917.

' //4 van for:

6/4 air/es Laodmm UNITED? STATES; PATENT oFFrcE.

CHARLES L. GOODRUM, OF'BROOKLYN, NEW YORK, ASSIGNOR.TOWESTERNTELEC'IRIG. COMPANY, INCORPORATED, OF NEW YORK, N. .Y., A CORPORATION. OF NEW' YORK.

MACHINE-SWITCHING TELEPHONE-EXCHANGE SYSTEM-.3

Specification of Letters Patent.

Patented A'ng.'28,'1917.

Application-filed October 2, 1916. Serial No. 1233, 111.v

1 '0 all whom it may concern Be it known that I, ca ms L. GoonuUi-r, a citizen of the United "States, residing at subscribers are automatically debarred from.

using such trunks.

In accordance with this invention the terminals of the restricted lines-have impressed upon them current: (littering in character from that impressed upon those of the nonrestricted lines, anda'relay is associated with the calling line terminal and operated or not, accordingto the characterof current impressed upon such terminal; This relay, in operating, prepares a circuit "which is closed when the automatic switch is set in operative relation to theoutgoing trunk group, which circuit includes an electromagnet which operates and renders inoperative the secondary magnet stepping-circuit, which is ordinarily automatically closed when the outgoing.,.trunk grou is selected.

More specifically, the-lines o 'Jtherestricted subscribers are'providedwith test terminals which are connected to the opposite pole of the battery from that to which similar test 'termina'lsof the lines of the nonrestricted subscribersareconnected, and a polarized relay is' associated with the connector which operates, or not, accordingto the character of the calling line, and either prepares-a circuit'which, when the connector is set upon the outgoingtrunk group, disables the connector and givesa busy sig-, nal back to'the calling party, or permits the trunk call to be made, dependingupon the character of the callingline.

Referring to the draw1ng,wh1ch IS a diagram of a circuit arrangementembodying.

the invention, the invention-Willbe more readily understood by describing :in detail the operation.

. Upon the removal ofthe receiveratsubstation A, the line relay LR lbecomes energized, and in the well-known manner,xstarts a line finder LF' in'motion, seeki'ngthe cal-l v ing line. When the finder brushes 1, 2,3

come to rest upon the calling. line multiples 4, 5, 6, the cutoil relay CO is energized toremove the control of the line relay LR from. the calling party. Assuming. substation A' to he a non-restricted line, the polarized re--- lay 7 connected to the finder test-brush 3 is notoperated. The callingrparty-now actuates the sender to operate thevstepping,

'70" relation to the group containingqthecalling, When the relay S'becomes energized.

relay 8 to set the connectorC inoperative lllle. as the finder connects With thezcalling line, a

slow relay 9 is operated by the attraction of the armature ofsuch-stepping relay; When,

over the following, path to the primary magnet PM .ofthe connector: ground,- armature and back contact of'relay 8, right arma ture and front'contact "of relay 9, conductor 10,'connector side-switch arm 11' and its first contact, .magnet' PM, right armature and back contact of busy relay BR, free poleof battery. Upon thefirst' retraction of the.

armature of stepping relay 8, a relay 13 is energized, and beingslow acting, remains energized while the armature of'relay 8-1ssender- S reaches itsnormal position and.

.95 attraction of the armatureof relay 8 causes Y maintains relay 8 energized, the maintained the dcenergization ot relay'lil, which in re+ tracting itsarmature, deenergizes the escape magnet which releases theside switch into position 2.

The callingparty now operates the sender S to transmit the units digittot "the called number. Upon each retraction of the armature of relay 8, animpulse is sent over arm 41 to the secondary magnet'SM, the circuit including the right armature and backcontact of relay-'BR.- MagnetSM'thus steps the brushes 16,17, 18 over the selected .75; now, the sender S interrupts the line circuit, is upon each retract-ion. of the armature of 're-' lay 8, an impulse of current istransunttedgroup of multiples containing those of the wanted line 19, 20, 21. Upon the first retraction of the armature of relay 8, slow relay 13 again energizes, and in attracting its right armature, energizes the escape magnet. Upon the maintained energization of relay 8, as the sender restores, slow relay 13 becomes de'energized, and in retracting its right armature, deenergizes the escape magnet which releases the side switch into position 3, assuming the line to be idle, which is the case if no ground is present on test multiple 21. As the arm 29 reaches its third contact, ground is applied to the test multiples 21 of the selected line to cause the same to test busy to other connectors and to operate the cutoff relay of. such line. In position 3 the escape magnet is again energized over a circuit including arm 22 and the armature and back contact of ringing cutoff relay RCO. The escape magnet, in attracting its outer armature, applies ringing current to the called line over the following circuit: free pole of ringing gener tor 23, relay RCO, outer armature and front contact of magnet -15, arm 21 and its third contact, brush 17, multiple 20, bell 25, condenser 26, multiple 19, brush 16, arm 27 and its third contact to ground.

'hen the called party removes his receiver, relay RCO attracts its arn'iature, opening the circuit of the escape magnet, which in denergizing, releases the side switch into position t, in which position talking current is fed to the called substation B over the following circuit: free pole of battery, left winding of feed coil 28. arm 27 and its fourth contact, brush 16, multiple 19, through the telephonic apparatus at substation B, multiple 20, brush 17, arm 24 and its fourth contact, right winding of feed coil 28 to ground.

Upon the conclusion of the conversation the subscribers replace their receivers. Relay 8, in retracting its armature, opens the circuit of relay 9, which, after a slight interval, retracts its armatures, whereupon the following circuit is closed for the release magnet R'M of the connector, and Rh[ of the finder: armature and back contact of relay 8, inner armature and back contact of relay 9, where the current divides, part passing by way of the outer armature and back contact of relay 9. otf-normal contact ION of the finder, to the magnet RM of the finder, the remainder passing by way of conductor 30, off-normal contact PO'N to the release magnet R'M of the connector. Magnet RM then locks itself up in a circuit including off-normal contact PON. When the connector brush shaft reaches its normal position, it opens the off-normal contact PON. thus opening the locking circuit of the magnet RM, and when the finder brush shaft reaches its normal position, it opens ofi-normal contact PON, whereupon the release magnet RM of the finder becomes deenergized.

If the selective line is busy, the multiple 21 is grounded, and when the test brush 18 reaches such multiple and before the escape magnet 45 becomes de'e'nergized, after slow relay 13 opens its circuit, the following circuit is closed for the busy relay BR: ground, multiple 21, brush 18, arm 29 and its second contact, spring 31, controlled by the brush shaft, now closed, to its lower contact, inner armature and front contact of escape magnet 4-5, inner armature and back contact of slow relay l3, conductor 30, rigl'it winding of relay BR, free pole of battery. Relay BR, in attracting its inner armature, locks itself to ground at the armature and front contact of relay 8, and in attracting its outer armature, connects a source of busy tone signaling current 32 to talking conductor 23, and thence to the calling line, to indicate to the calling party that the desired line is busy. -Wl1en the calling party replaces his receiver, release takes place as hereinbefore described.

Assuming now that the calling party desires a connection with a trunk leading to the main ottice to which the private branch exchange shown belongs. In that event, the calling party operates his sender to set the connector (l in operative relation to the tenth or top group of terminals in the connector. \Vhen. the' connector is so set, contact. 31 is closed, and spring 31 is shifted to its upper contact by the connector brush shaft. Now, when the slow relay 13 deenergizes as the sender reaches its normal position, the following circuit is closed to energize relay permanently grounded terminal 36, with which brush 18 engages at the end of the primary movement of the brush shaft when the outgoing trunk group is selected, brush 18, arm 29 and its second contact, spring 31 now closed to its upper contact, relay 35, free pole of battery. Relay 85, in attracting its inner left armature, again energizes slow relay 12-5 to energize theescapc magnet 45, and in attracting its right armature, (loses the following self-interrupting circuit for magnet SM: free pole of battery, right aru'iaturc and. back contact of relay BR, magnet SM and its armature and back contact, arm 3'? and its second contact, right armature and front contact of relay 3:) to ground. The brushes- .16, 17, 18 are thus stepped over the trunk group in search of an idle trunk which is indicated by the absence of ground on the test multiple -18 thereof. 'hen the test brush 18 encounters such ungrounded test multiple, relay' 35 becomes deenergized, and in retracting its right armature, opens the circuit of magnet SM, thus stopping the brushes upon the seized trunk terminals,

and in retracting its-inner-left armature, opens the circuit of relay 13, which in deenergizing, opens the circuit of escape magnet 45 which releases theside switch into position 3. In position 3, the escape magnet is again energized over a circuit including arm 22 and the armature and back contact of relay RCO, as described. in connection with a call for a party in the private branch exchange, which results inringing current being applied to the seized trunk to oper ate a signal attheoperators position to indicate the arrival of acall. The operator responds to such signal by suitable means, and extends'the call-in the wellknown manner.

Assuming now that a restricted subscriber attempts to secure a connection with the central oflice. The;lines of such subscribers are provided with cutoff relays CO, connected to the opposite-pole of batteryfrom that to which the cutoff relays CO oft-he non-restricted subscribers are connected. The polarized relay 7 is adapted torespond and close contact 43, when-the finder. brush 3 engages the-test multiplef38 of. the restricted lines.

\Vhen the calling party sets the connector in operative relation to the outgoing trunk group, the contact 34 is closed by the connector brush shaft, and'the following circuit is closed for the relay'BR: free pole of battery, left winding 0f-relay BR, conductor 39, outer armature and back contact of relay 13, contact 34, toground at the armature of thepolarized:relay 7. Relay- BR, in attracting its rightwarmature, o Jens the connection of battery to the secont ary stepping magnet SM, thus preventing the trunk hunting operation from taking place, and in attracting its outer left armature, connects a busy tone to the calling line to indicate to the calling party that the connection cannot be had. "The relay BB in attracting its inner left armature, locks itself to groundat the armature and front contact of'relay 8. 'IVhen-the-calling party replaces his receiver,-the relay 8, in retracting its -arinature,-opens the circuit of relay 9. The retraction of the armatures of relay 9 closes the circuits of release magnets R'M' of the connector and 'RM of the finder, as hereinbefore described. \Vhen the connector brush shaftreaches its normal position and opens contact'PO'N. .the magnet RM is deenergized. Similarly, when the finder brush-shaft reaches itsnormal position and opens contact PON,'the magnet'RM. isdeener ized.

hat is claimed is:

1. In a telephone exchange-system, :the combination with telephone lines of different classes, tQIHllHfllS'fOI'SfiiCl lines, means for impressing current of one character on terminals of lines of one class=and of another character on those ofthe other class, a group of trunk lines, an automatic switch wherein said trunk lines terminate, primary and secondary inagnetsfor said switch, a

- source of currentltherefor, a relay, means for extending the calling line to said switch and for connecting said relay .to the terminal of such line,- said relay operating, or

not, according to the currentimpressed on said terminal, means for setting saidswitch in operative relation to said trunlcgroup, and means thereupon automatically operated if said relay is energized, adapted toopen the connection of saidsource with. said' secondary magnet.

2. In a telephone exchange systemythe combination with restricted ;:and non-restricted telephone lines, a source ofv current, terminals for said lines, theternnnals of the restrictedlines being connected tothe opposite pole ofthe battery fIOlllxtllOSG of the non-restricted lines, agroup of" trunk lines, an automatic switch wherein said trunk linesterminate, a polarized --relay, means for extending the calling line to said switch and for connecting said relay. to I the terminal of such line, said relay operating, or not,-according to the potential. impressed thereon, means for setting said switch in said switch, a polarizedrelay, means for'extending the calling "line to said switchrand for connecting'said polarized relay to the terminal of such line,-said-relay operating, or not, according tothe potential'impressed on said terminal, a sender for operatingsaid primarymagnet to set-said switch in operav tive'relation to said trunkgroup, and means thereupon automaticallyoperated either to open the connection of said-secondary magnet with saidsourcc of current or'to cause said magnet todrive the connector over said;

trunk group, dependent uponthecondition of said polarized relay.

4. In a telephone exchange system, the combination with restricted and .non -'-restricted subscribers lines,: a source of cur rent, test termlnals for said l1nes,the-test terminals of the restricted lines being con- 'nected to the opposite pole of -the- .battery from those of the non-restricted lines, a group of trunk lines, a connector wherein'said,

trunks terminate, primary and secondary driving magnets for said connector, a local driving circuit for said secondary magnet to cause said connector to test said trunks, a polarized relay, means for extending the calling line to said connector and for connecting said relay to the calling line test terminal, said relay operating if the line is a restricted line, a relay associated with said connector and adapted to render inoperative the actuating means for said secondary magnet, a circuit for said relay including a contact of said polarized relay and a contact operated by the connector shaft and closed when the connector is set in operative relation to the trunk group.

5. In a telephone exchange system, the combination with restricted and non-restricted subscribers lines, cutoff relays and test terminals therefor, the test terminals and cutoff relays of the restricted lines being connected to the opposite pole of the battery from the test terminals and cutoff relays of the non-restricted lines, a connector wherein said lines terminate, primary and secondary stepping magnets therefor, a sender adapted to operate said magnets to set said connector on any line, a. group of trunks terminating in said connector, :1 self-interrupting circuit for said secondary magnet adapted to cause said connector to test said group automatically, a polarized relay, means for extending the calling line to said connector and for connecting said relay to the calling line test terminal, said relay operating if the line is a restrictedline, a relay associated with said connector and adapted to open said self-interrupting circuit, a circuit for said relay including a contact of said polarized relay and a contact operated by the connector shaft and closed when the connector is set in operative relation to said trunk group.

6. In a telephone exchange system, the combination with subscribers" telephone lines divided into classes, a connector, a driving magnet therefor, a group of trunks terminating therein, a sender associated with the calling line for controlling said magnet to set'said connector in operative relation to said trunk roup, driving means thereupon automaticalIy operated to cause said connector to test said group, a relay adapted to render said driving means inoperative, means associated with the calling line and dependent upon its character for controllin said relay and means controlled by the calIing party for thereafter releasing the connector.

7. In a telephone exchange system, the con'ibination with telephone lines divided intoclasses, test tOIll'llIHtlS therefor, sources of current of different character connected thereto, a connector, a driving magnet therefor, a group of trunks terminating in said connector, a sender associated with the calling line for controlling said magnet to set said connector in operative relation to said trunk group, driving means thereupon automatically operated to cause said connector to test said group, a relay adapted to render said driving means inoperative, and means for operating said role), or not, dependent upon the character of the current impressed upon the test terminal of the calling line.

8. In a telephone exchange system, the combination with restricted and non-restricted subscribers lines, test terminals therefor, means for impressing current of ditl'erent character upon said test terminals, a connector, a group of trunks terminating therein, prin'iary and secondary stepping magnets t'or said connector, a sender adapted to operate said magnets to set said connector on any line, a selt-interrupting circuit for said secondary magnet, a discriminating relay (7), means for extending the calling line to said connector and for connecting said relay to the calling line test terminal, said relay operating if the line is a restricted one, a relay (35) associated with said connector for closing said self-interrupting circuit,

said relay operating when the trunk group is selected and being maintained energized as long as lousy trunks are encountered, and a relay (BR) operated when the trunk group is selected by a restricted line and disabling said self-interrupting circuit.

In witness whereof, I hereunto subscribe my name this 29th day of September, A. D. 1916.

CHARLES L. GOODRUM. 

